Category: Biological Sciences

Lauren Ammerman: Reversing Multidrug Resistance in Cancer through Iterative Identification of P-glycoprotein Inhibitors

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Winner: Biological Sciences (Graduate)

co-authors: James McCormick (co-first author), Chanyang Park, Courtney Follit, Jesiska Lowe, Pia Vogel, and John Wise.

Multidrug resistance (MDR) describes the intrinsic or acquired resistance of cancers to diverse chemotherapeutics and is arguably one of most significant barriers to cancer treatment. As a mechanism of MDR, cancers commonly overexpress ATP-binding cassette transporters such as P-glycoprotein (P-gp). P-gp harnesses the power of ATP hydrolysis to efflux cytotoxic compounds across the cell membrane. Inhibition of P-gp can re-sensitize cancers to chemotherapeutics, but many P-gp inhibitors are also transport substrates of P-gp. Consequently, high compound dosages can be required to inhibit P-gp, and this can result in toxic off-target effects. To identify potential P-gp inhibitors that are not transport substrates, we iteratively screened millions of compounds against dynamic P-gp targets using massive parallel docking experiments. Hits from computational screens were then subjected to QSAR and purchased for testing. Compounds were assessed for their ability to reverse MDR using two sets of paired, human cancer cell lines – two chemotherapy resistant, P-gp overexpressing lines, and two chemotherapy-sensitive, non-P-gp overexpressing lines. Compounds were then tested for inherent toxicity against a non-cancerous human cell line. Lastly, we determined if our putative inhibitors are P-gp substrates using LC-MS/MS intracellular accumulation assays. We report a global hit rate of 15%.

Lauren Ammerman
Program: PhD in Biological Sciences
Faculty mentor: John Wise

Daniel Chavez and Eli Laird (U): An ODE-Based Model for the Spread of COVID-19 at Southern Methodist University

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Co-authors: Eli Laird

In early 2020, the SARS-CoV-2 outbreak made its way into the United States and began to rapidly breach all existing protocols for dealing with an infectious disease spreading within communities both locally and at large. As a result all academic institutions within the United States disbanded their campus and school communities so as to slow the spread of the novel virus. We modified a standard Susceptible-Exposed-Infected-Recovered (SEIR) compartmental model to examine the intertwined behaviors of both residential and community populations within university and college campuses, with a focus on Dallas' Southern Methodist University. The modified model contains a new quarantined/isolation category and an equilibrium between the susceptible and exposed categories, with a novel exposure function linking the two. Exposure rates for relevant spaces where students frequently flow through were predicted and calculated from official SMU databases and floor plans. These predictions may be used to propose disease-prevention strategies specific for college campuses.

Daniel Chavez
Majors: BS Biochemistry & BBA General Business
Faculty Mentor: Brandilyn Stigler

 

Rebekah Napier-Jameson: RNA binding proteins coordinately control lifespan in C. elegans

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Co-authors: Victoria Schatzman, Adam Norris

In order to identify genes that coordinately control gene expression with important phenotypic consequences, we performed a CRISPR/Cas-9 based Synthetic Genetic Interaction (CRISPR-SGI) screen in C. elegans. We focused on conserved neuronally-expressed RNA binding proteins, and identified many double mutants with unexpected fitness defects. In one notable interaction between the MBNL1/2 ortholog mbl-1 and the ELAVL ortholog exc-7, double mutants displayed a severely shortened lifespan (~70% decrease). We have used RNA-Seq data to investigate which RNAs may be uniquely dysregulated in the double mutant. nhx-6, a predicted Na/H exchanger, which was identified from our RNA Seq data contributes to the phenotype and is expressed in the intestine. mbl-1 and exc-7 are neuronally-enriched genes. Initial experiments have shown partial rescue of the lifespan phenotype with mbl-1 re-expression in the nervous or intestinal tissues of the double mutant but not muscle tissue. Shortly we will be conducting experiments to test whether exc-7 expression in the nervous system is the critical tissue affecting whole-worm lifespan. Through these studies we hope to identify how these RNA binding proteins are contributing to the lifespan phenotype seen in the mbl-1;exc-7 double mutants.

Rebekah Napier-Jameson
Program: PhD in Biological Sciences
Faculty mentor: Adam Norris

Kelsey Paulhus: Leading with the head or heart? Deciphering the specific roles of Kv1.1 in cardiac function, epilepsy, and SUDEP

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Co-authors: Krystle Trosclair, Man Si, Megan Watts, Kathryn A. Hamilton, Md. Shenuarin Bhuiyan, Paari Dominic, Edward Glasscock

Mutations in ion channel genes with brain-heart expression patterns have been proposed as risk factors for sudden unexpected death in epilepsy (SUDEP) since they can cause both seizures and lethal cardiac arrythmias. One such gene is Kcna1, which encodes voltage-gated Kv1.1 potassium channel α-subunits. Kcna1 global knockout (KO) mice recapitulate many features of human SUDEP including frequent generalized tonic-clonic seizures that cause cardiorespiratory dysfunction leading to sudden death in about 80% of animals. Neuron-specific Kcna1 conditional KO (cKO) mice also exhibit premature death, epilepsy, and cardiorespiratory dysregulation, but to a lesser degree than global KOs, suggesting that Kv1.1-deficiency in the heart may cause intrinsic cardiac dysfunction that increases risk of mortality. Here we restrict Kv1.1 deficiency to heart tissue using a newly generated Kv1.1 cardiac cKO mouse to elucidate the contribution of Kv1.1 both to overall cardiac electrophysiology and how cardiac-specific deficiency contributes to the cardiac abnormalities and SUDEP risk seen in global KO and neuron-specific cKO mouse models. Our findings indicate that while Kv1.1 plays a functionally significant role in cardiomyocytes, the cardiac and sudden death phenotypes observed in the global KO and neuron-specific cKO mice are largely brain-driven.

Kelsey Paulhus
Program: PhD in Biological Sciences
Faculty mentor: Edward Glasscock